feat: add tox-args support for custom CLI flags

[rnetser]

Problem

Currently the tox configuration only maps branches to test environments. There's no way for users to pass custom CLI flags to tox (e.g., -p for parallel, -x for fail-fast).

Proposed Solution

Add a tox-args configuration key:

tox:
  main: all
tox-args: "-p -x"

Requirements

• Add tox-args to config schema (webhook_server/config/schema.yaml)
• Read tox-args in github_api.py _repo_data_from_config()
• Pass args to tox command in runner_handler.py run_tox()
• Add tests for new functionality
• Update example config

[rnetser]

duplicate o fhttps://github.com//issues/1092